Combined froth-pour spray system for resin foams

ABSTRACT

Apparatus for processing an organic resin froth from an airlesstype spray gun employing an adapter which has a second mixing chamber coaxial with the spray axis of the gun, together with means for selectively introducing either a pressurized mixture of a physical blowing agent to create a froth from the material issuing from the spray gun or a solvent for cleaning the second mixing chamber at the conclusion of the spraying operation.

United States Patent McCain COMBINED FROTH-POUR SPRAY SYSTEM FOR RESINFOAMS Samuel B. McCain, Bothell, Wash.

Kir-

lnventor:

Assignee: Vertecs Corporation, Inc.,

kland, Wash.

Filed: Dec. 7, 1970 Appl. No.: 95,439

US. Cl. ..239/ll2, 239/117, 239/123, 239/412, 239/4175, 239/4275 Int.Cl. ..BOSb 15/02 Field of Search ..239/112, 117, 123, 400, 407, 239/412,417.5, 427.5, 428, 429, 433;

264/54; 260/26 BD, 2.5 BC

References Cited UNITED STATES PATENTS Gusmer ..239/ 142 X Hoppe et a]...260/2.5 BC Perrin ..260/2.5 BC Wilson ..239/1 12 X 1451 Sept. 12, 19723,462,083 8/1969 Kautz ..260/2.5 BC

1,005,640 10/191 1 Gardner ..239/1 17 1,448,106 3/1923 Binks ..239/4002,539,314 1/1951 Murphy ..239/400 OTHER PUBLICATIONS Frothing RigidUrethane Foams, article in January, 1964, issue of Plastics Technology,pages 35- 37.

Primary Examiner-M. Henson Wood, Jr. Assistant Examiner-Edwin D. GrantAttorneyHill, Sherman, Meroni, Gross & Simpson [57] ABSTRACT Apparatusfor processing an organic resin froth from an airless-type spray gunemploying an adapter which has a second mixing chamber coaxial with thespray axis of the gun, together with means for selectively introducingeither a pressurized mixture of a physical blowing agent to create afroth from the material issuing from the spray gun or a solvent forcleaning the second mixing chamber at the conclusion of the sprayingoperation.

3 Claims, 2 Drawing Figures COMBINED FROTH-POUR SPRAY SYSTEM FOR RESINFOAMS BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention is in the field of foamed organic resins and is primarilyconcerned with adding the capability of frothing to a standardspray-type resin gun, which capability is accomplished by adding anadapter unit which receives the material discharge from the gun andconverts it to a froth by the metered injection of a physical blowingagent into the chemicals as it issues from the gun.

2. Description of the Prior Art The field of foam plastics or cellularplastics as it is sometimes called has advanced significantly since theearly 1950s when it was first introduced. Foamed plastics have been madefrom material such as cellulose acetate, polystyrene, and polyethylene,but by far the most prevalent foam system currently used is thepolyurethane system. A polyurethane foam system usually consists of twoliquid components, polyols and isocyanates which react together rapidlyto form a foam. Such compositions may also include additives such asemulsifiers, blowing agents, catalysts and modifiers.

There are three types of urethane foam, namely, rigid, semiflexible andflexible. The three types of foam have distinct advantages in a widevariety of applications. Because of its closed cellular nature, rigidfoam is particularly valuable for construction, flotation applicationsand for insulation.

Since the urethane foaming process is generally quite rapid, the variousproduction systems which have evolved require specialized equipment for-metering and mixing the components. The ratio of components is fixedfor any given system, so accurate metering is essential and thecomponents must be thoroughly and almost instantaneously mixed.

One of the widely used techniques for depositing urethane foam is theso-called pour-in-place system. In this process, the foam systemcomponents are metered, mixed and dispensed as a liquid stream into acavity where they react and expand to fill the void. The cavity may bean irregularly shaped mold, or a narrow panel, or the free space betweentwo walls. Since considerable pressure may be generated during thefoaming process, restraining jigs are usually used to maintain thedesired dimensional shape until the foam has set. The period for settingmay vary from about 5 to 30 or more minutes.

A second type of process for depositing urethane foam is the sprayingprocess. Urethane foam systems may readily be sprayed using specialspray guns which perform the dual function of mixing and atomization.Spray guns designed for this purpose may contain a mixer or the mixingmay be accomplished by turbulence of the liquid components supplementedby the air mospheric conditions. The advantages of frothing are lessleakage from small cracks in the cavity into which the froth is applied,rounder cells with somewhat greater strength in the transversedirection, slightly lower overall densities, and usually slightly lower.pressure.

The particular. installation involved will usually dictate the choicebetween the pour-in-place, the spraying and the frothing systems.However, a contractor should have equipment available for performingmore than one of these processes if required. Since the equipment isquite expensive, however, not all contractors are prepared to providethis capability.

One of the most widely used and successful spraying systems for urethanefoams is the Gusmer system marketed by the Gusmer Corporation of OldBridge, New Jersey. The Gusmer gun, as shown in and described in US.Pat. Nos. 2,890,836 and 3,263,928, is a positive displacement, airlesstype gun in which a reciprocating piston slides within the mixingchamber and the gun nozzle. When the piston is retracted, inlet portsare exposed to the mixing chamber, and the reactants (polyol andisocyanates) are than injected into the mixing chamber in a turbulentmotion, under pressure, and issue from the nozzle as a finely dividedspray. The air pressure actuated piston is then moved into the mixingchamber, closing off the inlets at the conclusion of the spraying operation, providing the device with a selfcleaning feature which is adefinite advantage over other types of spray guns heretofore used.

SUMMARY OF THE INVENTION The present invention is directed to an adapterwhich can be used in conjunction with the aforementioned Gusmer type gunor other airless, positive displacement type of spray gun to processfroth chemical formulations, thereby increasing the functionalcapability of the gun at a relatively modest cost. The adapter includesa body portion which is arranged to be fixedly secured against the headof the spray gun, and has an open ended mixing chamber which is coaxialwith the material axis emanating from the spray 'gun. A peripheral inletis formed about the mixing chamber and serves to introduce a physicalblowing agent underpressure into the mixing chamber. The resultingexpansion of the liquefied blowing agent-serves to form a froth whichissues from the end of the mixing chamber and may be applied to the jobsite. When the spraying operation is completed, the inlet is selectivelyconnected to a source of solvent which introduces a stream of thesolvent into the mixing chamber to wash the same clean of any adherentmaterials.

tion will be readily apparent from the following used for atomization.In airless guns, opposed jets of components insure thorough mixing, andthe high pressure fan issuing from the spray tip induces atomization.

A third system for applying polyurethane foam is the frothing system inwhich the partly reacted components are dispensed from the mixing headin a partially expanded state. This is accomplished either by preheatingthe components or by introducing a blowing agent which is a liquid underpressure but a gas under atdescription of certain preferred embodimentsthereof, taken in conjunction with the accompanying drawings, althoughvariations and modifications may be effected without departing from thespirit and scope of the novel concepts of the disclosure, and in which:

FIG. 1 is a partly schematic view, partly in elevation and partly incross-section illustrating a froth-pour system of the present invention;and

FIG. 2 is a fragmentary cross-sectional view of the mixing chamberwithin the spray gun itself.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeralindicates generally a spray gun embodying the type of construction whichhas been marketed heretofore by the Gusmer Corporation. This structureis merely illustrative of the invention since any airless type spray gunused for spraying foamable resin compositions can also be used. The gun10 includes a handle 11 with which there is associated an air valve 12having an operating button 13. The valve 12 is located in'a compressedair line 14 which provides air under pressure from any suitable source(not shown). Upon pressing the operating button 13, compressed air isadmitted into the interior of the gun through an inlet port 15 where'itacts against the face of a piston 16 reciprocable within the gun body.To the piston is attached a plunger '17, the latter extending through asleeve 18 connected to the body of the gun. An adjustment nut 19 islocated behind the piston 16 to adjust the amount the free end of theplunger 17 extends through the spray head, as will be apparent from asucceeding portion of this description. Av coiled spring'20 acts againstthe adjustment nut 19 and has one end bottomed against the rear end ofthe gun housing. Extending axially into the gun housing is an adjustmentbolt 21 which serves as a stop to limit the extent of rearward travel ofthe piston and plunger assembly.

The free end of the plunger 17 passes through a gland. nut 22 and isreceived within a spray head generally indicated at reference numeral 23in the drawings. The end of the plunger 17 is slidably received alongthe wall 24 of a mixing chamber formed in the spray head 23. The tworeactants for the polyurethane resin forming reaction, the polyol andthe isocyanate, are separately delivered under pressure by means ofconduits 25 and 26 to inlet ports 27 and 28 as shown in FIG. 2 of thedrawings. These ports are formed to inject the reactants generallytangentially to the mixing chamber 24, so that in entering the mixingchamber, a substantial amount of turbulence is created which serves toprovide efficient mixing of the ingredients and rapid initiation of theresin forming reaction.

Material processing is initiated by operating the button 13 so thatcompressed air forces the piston 16 rearwardly against the bias providedby the spring 20. .In doing so, the movement of the piston 16 causes theplunger 17 to be moved backwardly in the mixing chamber 24 therebyuncovering the inlet ports 27 and 28 so that the reactants arethoroughly mixed and then issue through the spray orifice at the frontof the gun. To terminate the material process operation, pressure on thebutton 13 is released whereupon the plunger 17 is forced forwardly toclose off the inlet ports 27 and 28 as shown in FIG. 2. The rubbing orsliding action of the plunger 17 against the wall of the mixing chamber24 serves to remove any accumulated material and provides'this type ofgun with a self-cleaning feature.

The adapter provided in the present invention to convert the sprayoperation to a frothing operation includes a body portion 29 which issecured to. the spray head 23 by means of bolts 30 or the like.interposed between the body portion 29 and the spray gun itself is asealing ring such as an O-ring 31.

Formed in the body portion 29 is a mixing chamber 32, the chamber 32being coaxial with the spray orifice from the spray gun 10 so that itreceives the discharge issuing from the spray head. At the periphery ofthe mixing chamber 32 is an inlet 33'which is arranged to introduceeither a physical blowing agent under pressure, or a cleansing solvent.As illustrated schematically in FIG. 1, the mixing chamber 32 isconnected by means of a conduit 34 to a check valve 35. Feeding thecheck valve 35 is a line 36 which is connected to a shutoff valve 37located in series with a preset metering valve 38. The latter isconnected by means of a line 39 to a supply of normally liquid blowingagent.

There are many physical blowing agents used to create froth in resinouscompositions. Typical among these are the aliphatic hydrocarbons such aspentane, neopentane, hexane, isohexane, heptane, and isoheptane.Aromatic hydrocarbons such as benzene and toluene have also beenemployed for this purpose. Halogenated hydrocarbons such as methylenechloride, trichloroethylene and symmetrical dichloroethane have alsobeen used. Of particular importance are the aliphatic fluorocarbons suchas dichlorotetrafluoroethane, trichlorofluoromethane andtrichlorotrifluoroethane and mixtures of these fluorocarbons.

The normally liquid blowing agent is injected into the mixing chamber 32by the action of a compressed air source (not shown) which is controlledby a shut-off valve 40.

Also feeding the check valve 35 is a supply of solvent for the reactantswhich appear in the mixing chamber 32. The supply of solvent (not shown)is under the control of a shut-off valve 41.

In operation, to produce a froth, the operating button 13 is depressed,while opening the air supply shutoff valve 40 and the blowing agentshut-off valve 37. The combination of the ingredients, the urethanefroth chemicals as delivered by the spray gun, the compressed air, andthe blowing agent produces a froth urethane foam in the mixing chamber32 which can be directed into the particular void to be filled.

The ratio of blowing agent can be adjusted by the preset metering valve38. After delivery of the desired quantity of urethane chemicals andblowing agent, the equipment is shut off by releasing the button 13 andthe supply of blowing agent is terminated by closing the valve 37 Thisis followed immediately by opening the solvent supply shut-off valve 41to cause purging of the inlet to the mixing chamber 30 with a thoroughrinse of flushing solvent and compressed air. Following the solventrinse, the assembly is ready for another cycle of operation.

The adapter of the present invention utilizes the inherent advantages ofexisting equipment which is limited to spray application, and therebymakes it possible to manufacture froth systems without an additionalsubstantial investment in mixing equipment. The savings in equipmentoutlay, combined with the convenience of rapid and inexpensivechangeover to modify the standard spray gun to manufacture frothurethane renders. the adapter of the present invention an importantmodification to standard spray equipment.

I claim as my invention:

1. In a spray device of the type including a spray head, including afirst axially extending mixing chamber, means for delivering a polyoland an iso- 2. The spray device of claim 1 in which said inlet means ispositioned between said spray orifice and the inlet to said elongatedmixing chamber.

3. The spray device of claim 1 which includes a supply of solventselectively connectible to said inlet .means to direct a stream ofsolvent into said mixing chamber.

2. The spray device of claim 1 in which said inlet means is positionedbetween said spray orifice and the inlet to said elongated mixingchamber.
 3. The spray device of claim 1 which includes a supply ofsolvent selectively connectible to said inlet means to direct a streamof solvent into said mixing chamber.